BORON CARBIDE BASED CERAMIC COMPOSITES HOT PRESSED WITH ALUMINIUM ADDITIVE

Abstract

Ceramic composite materials consisting of B₄C matrix and Al₈B₄C₇ secondary phase were prepared by in situ reactive sintering of the initial powder mixture B₄C-Al with concentration from 5 to 25 wt.% Al sintering additives. The composite samples were hot pressed at the temperature of 1850 °C, pressure of 35 MPa, for 15 min in a vacuum atmosphere. The portion of Al₈B₄C₇ secondary phase increased from 3.3 to 22.1 wt.% when increasing the concentration of Al sintering additive from 5 to 25 wt.% Al. Significant improving of densification and mechanical properties was measured at increasing of Al sintering additive concentration from 5 to 10 wt.% Al. The highest average hardness of 28.74 GPa was achieved when adding 15 wt.% Al sintering additive. The fracture toughness increased with concentration of Al sintering additive in whole concentration range with the highest average value of 5.92 MPa.m^1/2 at 25 wt.% Al sintering additives.